i have a customer that says she has radiant heating in a bedroom ceiling, is this possible? (the ceiling is leaking water coming from roof) the entire ceiling has to be ripped down and new blue board and all that stuff but how can new blue board be put in if theres radiant heating im kinda confused help please?

I have an old victorian home that nothing is normal about its construction. I will be insulating the attic soon with cellulose insulation. I have airsealed the attic, but now need to add baffles between each rafter. The problem is every rafter is a different width. Some 8" some 24". There is a material that is used to walk on to protect floors during construction. It comes in rolls and is durable and moisture resistant. I planned on rolling it out cutting where the ceiling joists are and stapling there and the rafters. Is this okay? Otherwise what would be recommended. Currently there is between 1.5" and 3" in the attic. I am putting at least 12" more.